1. Field of the Invention
The invention relates to trapped fluid microsystems for acoustic sensing.
2. Discussion
The typical human cochlea operates over a two and a half decade frequency band, from 20 Hz-20 kHz, covers 120 dB of dynamic range, and can distinguish tones which differ by less than 0.5%. Sounds as quiet as 0 dB SPL (20 μPa RMS) can be heard. Humans are also able to discriminate sounds temporally with spacing as small as 10-20 μs.
The human cochlea is small, occupying a volume of about 1 cm3. The cochlea uses a mechanical process to separate audio signals into approximately 3000 channels of frequency information; it is a sensitive real-time frequency analyzer.
Marine mammals such as whales hear over an even broader band than humans, utilizing acoustic signals for communication (at low frequencies) and navigation (high frequency “SONAR”). One difference between submerged and in-air operation is that the middle ear impedance matching functions may be inactive or modified in marine mammals due to the different characteristic impedance of the environment.